Tiger Woods hit a shot on the 13th hole on Sunday, saw it was going left, and went to the ground as if he'd just been shot.
For some reason Woods' back seems to get exponentially worse when he hits horrendous shots like this one that went into the water. He hurt his back laying on a too-soft bed earlier this week (his words) and has been struggling with it all week.
After his round Woods called the issue (specifically on this shot) a back spasm.
Woods went on to make bogey on the 13th hole and trailed the lead by two at that point.